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M2 Neuron Brain Behavior > 9/12 Brainstem3 - Rasin > Flashcards

9/12 Brainstem3 - Rasin Flashcards

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1
Q

dorsal structures of pons

A
  1. facial colliculus (ventral aspect of 4th ventricle - choroid plexus-less; CP only found in part adj to medulla)
  2. hypoglossal trygone
  3. 3x cerebellar peduncles
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2
Q

relationship between pontine nuclei and cerebellar peduncles

A

transverse section : see large middle cerebellar peduncles made of axons and pontine nuclei

  • axons of cells in pontine nuclei make up contralateral middle cerebellar peduncle!
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3
Q

conduit function of pons

A

descending pathways

  • corticospinal/corticobulbar pathways
  • anterior corticospinal pathway

ascending pathways

  • DCMLS
  • spinothalamic tract
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4
Q

CN V

sensory/motor components

A

trigeminal nerve

both motor (tiny efferent)/sensory (huge afferent) components

sensory components of CN V

1. GSA (general somatic afferent) from face for

  • face x 3!!!
    • pain and temp
    • touch/pressure/conscious propriop.
    • subconscious propriop.
  • touch and pain for nasal sinuses, inside nose, inside mouth (oronasal mucous membranes/teeth), ant. 2/3 tongue
  • pain for supratentoria dura mater (ant. part)

motor components of CN V

1. SVE (special visceral efferent) : muscles from branchial arches

  • muscles of mastication
  • tensor tympani m.
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5
Q

peripheral branches of CN V

A

CN V has 3 peripheral branches

  1. V1 opthalmic division
  2. V2 maxillary division (incl upper teeth)
  3. V3 mandibular division (incl lower teeth)
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6
Q

nuclei of CN V

A

CN V has 4 nuclei (3 sensory, 1 motor)

1. spinal trigeminal nucleus : pain/temp

  • extends from pons through medulla to cervical levels (3 levels!)

2. chief/principal sensory nucleus : touch/pressure

  • pons only

3. mesencephalic nucleus : subconscious proprioception

  • extends from pons into mesencephalon

4. motor nucleus of V : muscles of mastication

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7
Q

trigemino-thalamic pathway

A

pain, temp, some touch

1st order neuron : trigeminal ganglion

  • descends and synapses on spinal nucleus

2nd order neuron : spinal nucleus of V (medulla)

  • decussation occurs at levels of pons and medulla (due to extended nature of nucleus) → cross to form trigeminothalamic fibers

3rd order neuron : VPM nucleus of thalamus

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8
Q

spinal trigeminal tract and nucleus

ipsi or contra?

where does decussation occur?

location/length

A

spinal nucleus carries GSA which conduct ipsilateral impulses of pain, temp, and some touch from head face and neck

  • ipsilat because decussation occurs when second order neurons cross over to contralat side on way to VPM of thalamus (AFTER they synapse at spinal nuc)

location: lateral to cuneate tract/nucleus

  • spinal tract superficial, spinal nucleus deep

extends form lower pons to upper cervical segments (C2-C3)

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9
Q

which artery affects pain and temp for face?

A

PICA!!!!

lateral medullary syndrome

  • would lose pain/temp sensation on ipsilateral face
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10
Q

spatiotemporal maps of spinal trigeminal nucleus

A

imagine taking widening ice cream scoops out of the face

  • scoop1 = nose/lips
  • scoop2 = eye/chin
  • scoop3 = top 2/3 of head/top of ear/chin
  • scoop4 = middle of ext surface

within the spinal trigeminal nucleus, there is a column of cells each for V1, V2, V3, VII/IX/X (ventral → dorsal arrangement)

  • the scoops are arranged 1-4 in a ventral→dorsal arrangement in each column!
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11
Q

what nerves (aside from V) contribute to the spinal trigeminal nucleus???

A

IX : sensation for back of ear, posterior 1/3 of tongue, upper pharynx (along with X/gagreflex)

  • this is how pain/temp for both ant 2/3 (V) and post 1/3 (IX) end up in the same place!

X : sensation for pharynx, larynx, ext ear and dura of post fossa

VII : GSA from back of outer ear

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12
Q

trigemino-lemniscal pathway

A

touch, pressure (vibration/proprioception)

1st order neuron : trigeminal ganglion

  • stays level and synapses on chief/principal trigeminal/sensory nucleus

2nd order neuron : principal sensory nucleus of V (pons)

  • decussation occurs at levels of pons → cross to form trigeminal lemniscus

3rd order neuron : VPM nucleus of thalamus

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13
Q

location of principal sensory nucleus

A

posterior to CST and pontine nuclei, slightly more lateral on dorsal side

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14
Q

mesencephalic nucleus of V

what is received?

what is the function?

where is it located?

A

unconscious proprioception & “jaw jerk reflex”

**ONLY NUCLEUS THAT CONTAINS PRIMARY SENSORY AFFERENTS**

  • jaw jerk reflex allowed for by connection of primary sensory afferents → motor nucleus of V

fx : controls the force of bite, conveys proprioceptive and pressure impulses from face

  • teeth, peridontium, hard palate, muscles of mastication, joint capsule via muscle spindles and other mechanoreceptors
    location: below superior cerebellar peduncles,
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15
Q

motor nucleus of V

A

innervates SVE : muscles of mastication and tensor tympani

  • located slightly more medially (motor!)
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16
Q

summary for nuclei of V

A

everything ipsilateral!

  • crossing occurs at neurons that project from the nuclei on up to thalamus/cortex
17
Q

CN V lesions

  • trigeminal neuralgia
  • causes of sensory loss to face
A
  • atrophy of affected side
  • deviation of jaw to affected side on opening (due to pterygoid muscles that draw mandible forward/midline)
  • loss of corneal/jaw jerk reflex

trigeminal neuralgia (Tic doloureux)

  • recurrent episodes of brief severe pain lasting from seconds to mins (V2-V3)
  • normal facial sensation
  • mostly unknown cause

sensory loss of face

  • trauma
  • metastatic disease
  • trigem/vestibular Schwannoma
  • meninioma
  • demyelination
  • aneurysom of petrous portion of ICA
  • infarcts
  • herpes zoster
18
Q

CN VII

components

A

facial nerve

carries both motor and sensory components

  • involves multiple brainstem nuclei, but axons come together to form a single nerve at level of pontomedullary jx

2 efferent motor components

1. SVE (special visceral efferent) for muscles from branchial arches…

  • muscles of facial expression, stapedius, part of digastric m.

2. GVE (general visceral efferent) to pregang PSNS to…

  • saliv/lacrim-ation : lacrimal, sublingual, submandibular, all other salivary glands (EXCEPT parotid - IX)

3 afferent sensory components

1. GSA (general somatic afferent) : sensation from small region near outer ear

2. SVA (special visceral afferent) : taste from ant 2/3 tongue

3. GVA (general visceral afferent) : some nasopharynx mucous membrane

19
Q

nuclei of VII

A
  1. motor nucleus of VII : SVE (muscles derived from branchial arches)
  2. superior salivatory nucleus : GVE (PSNS to salivary/lacrimation)
  3. rostral solitary nucleus : SVA (taste to ant 2/3 tongue)

honorable mention: spinal nucleus of V!

  • GSA from back of outer ear (along with IX and X)
  • crosses and ascends in trigeminothalamic tract to VPM_thalamus
20
Q

nucleus involved with CN VII motor fx

facial motor nucleus

location/structures associated

what is innervated?

A

facial motor nucleus

  • gives off axons that will loop around the abducens nucleus and form facial colliculus (bulging out of floor of 4th ventricle) in process
    innervates. ..
  • muscles of facial expression
  • stapedius
  • digastric
21
Q

need-to-know re: corticobulbar projection to motor nucleus of VII

A

UMNs from both ipsilat and contralat cortex synapse on LMN to upper face → bilat innervation

HOWEVER

ONLY UMN from contralat cortex synapse on LMN to lower face → contralat innervation only

implication: LESION THAT KNOCKS OUT UMN of one side will affect contralateral lower face!

  • will be able to move eyebrows, but not able to smile on one side
22
Q

reflexes involving motor nucleus of CN VII

A
  1. corneal → opthlamic nerve CN V (orbicularis oculi)
  2. sucking → mandibular nerve CN V (orbicularis oris)
  3. blinking_light → optic nerve CN II (orbicularis oculi)
  4. blinking_noise → cochlear nucleus CN VIII (orbicularis oculi)
  5. sound attenuation → cochlear nucleus (stapedius)
23
Q

nucleus involved with CN VII motor function

superior salivatory nucleus

what’s innervated?

A

GVE : pregang PSNS to lacrimal, nasal mucosa, submandibular/sublingual salivary glands

24
Q

nucleus involved with CN VII taste

A

rostral solitary nucleus

SVA (special visceral afferent) carrying taste from ant 2/3 of tongue

25
Q

CN VII lesions

Bell’s palsy

A
  • acute, overnight unilateral facial weakness (LMN)
  • retroauricular pain
  • hyperacusis (sometimes)
  • dry eye (sometimes)
  • loss of taste (sometimes)
26
Q

pons summary : locations of nuclei map

A
27
Q

vascular supply of pons

A

anterior circ : internal carotid artery

posterior circ : vertebral artery

basilar a. → paramedian branches will cover pons midline structures

  • CST, pontine nuclei, abducens nucleus

AICA and SCA → circumferential branches/lateral pontine aa. will cover pons lateral structures

  • facial nucleus, sensory nucleus of V, motor nucleus of V, and DESCENDING SYMPATHETIC FIBERS!!!!
    • sympathetic issues : Horner’s syndrome →
      • PSNS prevailing (miosis, ptosis, enopthalmose - sinking of eye)
      • low SNS (anhidrosis, hi skin temp, flushing of skin)
28
Q

dorsal view of midbrain

A

exit of CN IV

  • only CN to exit dorsally

4 bulbs (2 superior colliculi, 2 inferior colliculi) → “quadrigeminal”

  • SC associated with visual pathways
  • IF associated with auditory pathways
    • “eyes above ears”

both colliculi connected to diencephalon; cross midbrain-diencephalic jx via…

  • bSC (brachium superior colliculus)
  • bIC (brachium inferior colliculus)
29
Q

cerebral peduncles

A

CST and corticobulbar tract descend from internal capsule through cerebral peduncles

  • somatotopic organization: leg lateral, trunk middle, arm medial, face even more medial

corticopontine fibers descending to reach pontine nuclei to form the plan (“what do you want to do?”)

30
Q

lateral & anterior corticospinal pathways

A

control of fine movement

1st order : layer V cells of motor cortex (upper)

2nd order : ventral horn laminae VII, VIII, IX

3rd order : motor neurons of layer IX (lower)

  • lateral CST decussates in medulla
  • anterior CST crosses at spinal segmental layers
  • BOTH display somatotopic org
31
Q

descending pathways of midbrain

tracts (location?)

what do they control?

where do they decussate and descend?

A
  1. red nucleus (RN) aka “nucleus ruber” → rubrospinal tract
  • location of RN: behind cerebral peduncles and substantia nigra
  • control of contralateral extremities’ movement, esp FLEXORS
  • decussates in midbrain (ventral tegmental decussation) → contralateral rubrospinal tract

rubrospinal tract ends up descending in lateral column (v close to lat CST) → terminates at cervical levels

  1. tectospinal tracts
  • location: originates in superior colliculus of midbrain
  • controls coordination of head and eye movement
  • decussates in midbrain

ends up descending in anterior spinal cord → terminates at cervical levels

32
Q

summary of lateral and medial descending motor systems

A

rubrospinal tract ends up in lateral motor system

tectospinal tract ends up in medial motor system

33
Q

ascending pathways of midbrain

relation of two ascending pathways as you move up

implication for midbrain lesions

A

recall: when ascending, DCMLS and spinothalamic/anterolateral systems are…

  • far apart in spinal cord
  • far apart in medulla
  • closer together in pons
  • together in midbrain

implication: lesion affecting midbrain → all sensory modalities of contralateral side will be affected!

34
Q

nuclei of CN III

A

nucleus of CN III : motor is medial to sensory

  • superior to nucleus of CN IV
  • comprised of oculomotor nuclei & Westphal-Edinger nucleus
  • contains GSE and GVE (Westphal-Edinger nucleus : PSNS fibers → miosis in Horner’s syndrome)
35
Q

nucleus of CN IV

A

trochlear nucleus

  • inferior to motor nucleus of CN III (medial)
  • contains GSE → superior oblique m.
  • cross to contralateral side and exit on dorsal side
36
Q

nucleus of VI

A

NOT IN MIDBRAIN!!!

  • abducens nucleus in pons (surrounded by axons that comprise the facial colliculus!)
  • exits in midline at pontomedullary jx
37
Q

vascular supply of midbrain

which artery? why is it critical?

general coverage zones and arteries associated

A

posterior cerebral arteries → cerebral peduncles

  • lesions here have severe effects: all the tracts are jammed up close to one another in the midbrain!
    • motor: CST & CBT
    • all sensories (antlat, ML, trigeminal pathways all together)

COVERAGE

proximal PCA → cerebral peduncles, substantia nigra, sensory pathways, descending sympathetic fibers

paramedian branches at top of basilar artery → caudal portion of midbrain (medial)

SCA & prox PCA → posterior portion of midbrain

M2 Neuron Brain Behavior (53 decks)

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